Demodulation reference signal management in new radio

Abstract

Aspects of the present disclosure disclose techniques for implementing a wideband reference signal to improve the narrowband channel estimation performance associated with narrowband demodulation reference signal (DMRS) for the data channel in NR communications. Specifically, because the wideband reference signal may occupy wider bandwidth than the DMRS, the channel estimation realized may be more accurate than solely relying on the narrowband DMRS. In some examples, the wideband reference signal, which may be control reference signals (CRS), channel state information (CSI) reference signal (CSI-RS) in downlink or uplink sounding reference signal (SRS), may be associated with a corresponding narrowband DMRS in a data channel. The wideband reference signal may be either included in the control channel region or the data channel region.

What is claimed is: 
     
       1. A method for wireless communications, comprising:
 determining whether to include a wideband reference signal for data channel demodulation for a subframe based on a presence or absence of downlink data scheduled in the subframe; 
 associating the wideband reference signal with a narrowband demodulation reference signal (DMRS) in a data channel based on the determining, wherein the associating the wideband reference signal with the DMRS comprises attaching the wideband reference signal in a control channel region or a data channel region based on a determination that downlink data is present in the subframe; or omitting the wideband reference signal in the control channel region or the data channel region based on a determination that the downlink data is absent in the subframe; and 
 transmitting a notification to a receiving device that indicates whether the wideband reference signal can be used for data channel demodulation based on the association. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining whether a precoding for the wideband reference signal is different from the precoding for the narrowband DMRS; and 
 transmitting a first precoding vector for the wideband reference signal and a second precoding vector for the narrowband DMRS based on the determining, wherein the first precoding vector and the second precoding vector are either explicitly indicated or determined, or derived based on one or more conditions. 
 
     
     
       3. The method of  claim 1 , further comprising:
 identifying a precoding resource block group (PRG) size for the narrowband DMRS, wherein the PRG size allows for the receiving device to assume precoding granularity for multiple resource blocks based on the PRG size. 
 
     
     
       4. The method of  claim 3 , wherein the PRG size for open-loop multiple-input and multiple-output (MIMO) based DMRS is different than the PRG size for closed-loop MIMO based DMRS. 
     
     
       5. The method of  claim 4 , wherein the PRG size for the open-loop MIMO based DMRS is signaled to the receiving device using a one-bit indicator and the PRG size for closed-loop MIMO using a two-bit indicator. 
     
     
       6. The method of  claim 3 , further comprising:
 allocating resource blocks of a partial PRG to the receiving device, wherein the partial PRG allocated assumes same precoding for an entire PRG. 
 
     
     
       7. The method of  claim 1 , wherein the wideband reference signal occupies wider bandwidth than the narrowband DMRS. 
     
     
       8. The method of  claim 1 , wherein the wideband reference signal is one of a control reference signal or a channel state information (CSI) reference signal in downlink or SRS in an uplink communication. 
     
     
       9. An apparatus for wireless communications, comprising:
 a memory configured to store instructions; 
 a processor communicatively coupled with the memory, the processor configured to execute the instructions to: 
 determine whether to include a wideband reference signal for data channel demodulation for a subframe based on a presence or absence of downlink data scheduled in the subframe; 
 associate the wideband reference signal with a narrowband demodulation reference signal (DMRS) in a data channel based on the determining, wherein the associate the wideband reference signal with the DMRS comprises attaching the wideband reference signal in a control channel region or a data channel region based on a determination that downlink data is present in the subframe; or omitting the wideband reference signal in the control channel region or the data channel region based on a determination that the downlink data is absent in the subframe; and 
 transmit a notification to a receiving device that indicates whether the wideband reference signal can be used for data channel demodulation based on the association. 
 
     
     
       10. The apparatus of  claim 9 , wherein the processor is further configured to execute the instructions to:
 determine whether a precoding for the wideband reference signal is different from the precoding for the narrowband DMRS; and 
 transmit a first precoding vector for the wideband reference signal and a second precoding vector for the narrowband DMRS based on the determining, wherein the first precoding vector and the second precoding vector are either explicitly indicated or determined, or derived based on one or more conditions. 
 
     
     
       11. The apparatus of  claim 9 , wherein the processor is further configured to execute the instructions to:
 identify a precoding resource block group (PRG) size for the narrowband DMRS, wherein the PRG size allows for the receiving device to assume precoding granularity for multiple resource blocks based on the PRG size. 
 
     
     
       12. The apparatus of  claim 11 , wherein the PRG size for open-loop multiple-input and multiple-output (MIMO) based DMRS is different than the PRG size for closed-loop MIMO based DMRS. 
     
     
       13. The apparatus of  claim 12 , wherein the PRG size for the open-loop MIMO based DMRS is signaled to the receiving device using a one-bit indicator and the PRG size for closed-loop MIMO using a two-bit indicator. 
     
     
       14. The apparatus of  claim 11 , further comprising:
 allocating resource blocks of a partial PRG to the receiving device, wherein the partial PRG allocated assumes same precoding for an entire PRG. 
 
     
     
       15. The apparatus of  claim 9 , wherein the wideband reference signal occupies wider bandwidth than the narrowband DMRS. 
     
     
       16. The apparatus of  claim 9 , wherein the wideband reference signal is one of a control reference signal, or a channel state information (CSI) reference signal in downlink or SRS in an uplink communication. 
     
     
       17. A non-transitory computer readable medium for wireless communications, comprising code for:
 determining whether to include a wideband reference signal for data channel demodulation for a subframe based on a presence or absence of downlink data scheduled in the subframe; 
 associating the wideband reference signal with a narrowband demodulation reference signal (DMRS) in a data channel based on the determining, wherein the associating the wideband reference signal with the DMRS comprises attaching the wideband reference signal in a control channel region or a data channel region based on a determination that downlink data is present in the subframe; or omitting the wideband reference signal in the control channel region or the data channel region based on a determination that the downlink data is absent in the subframe; and 
 transmitting a notification to a receiving device that indicates whether the wideband reference signal can be used for data channel demodulation based on the association. 
 
     
     
       18. The non-transitory computer readable medium of  claim 17 , further comprising code for:
 determining whether a precoding for the wideband reference signal is different from the precoding for the narrowband DMRS; and 
 transmitting a first precoding vector for the wideband reference signal and a second precoding vector for the narrowband DMRS based on the determining, wherein the first precoding vector and the second precoding vector are either explicitly indicated or determined, or derived based on one or more conditions. 
 
     
     
       19. The non-transitory computer readable medium of  claim 17 , further comprising code for:
 identifying a precoding resource block group (PRG) size for the narrowband DMRS, wherein the PRG size allows for the receiving device to assume precoding granularity for multiple resource blocks based on the PRG size. 
 
     
     
       20. The non-transitory computer readable medium of  claim 19 , wherein the PRG size for open-loop multiple-input and multiple-output (MIMO) based DMRS is different than the PRG size for closed-loop MIMO based DMRS. 
     
     
       21. The non-transitory computer readable medium of  claim 20 , wherein the PRG size for the open-loop MIMO based DMRS is signaled to the receiving device using a one-bit indicator and the PRG size for closed-loop MIMO using a two-bit indicator. 
     
     
       22. The non-transitory computer readable medium of  claim 19 , further comprising:
 allocating resource blocks of a partial PRG to the receiving device, wherein the partial PRG allocated assumes same precoding for an entire PRG. 
 
     
     
       23. The non-transitory computer readable medium of  claim 17 , wherein the wideband reference signal occupies wider bandwidth than the narrowband DMRS. 
     
     
       24. The non-transitory computer readable medium of  claim 17 , wherein the wideband reference signal is one of a control reference signal or a channel state information (CSI) reference signal in downlink or SRS in an uplink communication. 
     
     
       25. An apparatus for wireless communications, comprising:
 means for determining whether to include a wideband reference signal for data channel demodulation for a subframe based on a presence or absence of downlink data scheduled in the subframe; 
 means for associating the wideband reference signal with a narrowband demodulation reference signal (DMRS) in a data channel based on the determining, wherein the means for associating the wideband reference signal with the DMRS comprises means for attaching the wideband reference signal in a control channel region or a data channel region based on a determination that downlink data is present in the subframe; or means for omitting the wideband reference signal in the control channel region or the data channel region based on a determination that the downlink data is absent in the subframe; and 
 means for transmitting a notification to a receiving device that indicates whether the wideband reference signal can be used for data channel demodulation based on the association. 
 
     
     
       26. The apparatus of  claim 25 , further comprising:
 means for determining whether a precoding for the wideband reference signal is different from the precoding for the narrowband DMRS; and 
 means for transmitting a first precoding vector for the wideband reference signal and a second precoding vector for the narrowband DMRS based on the determining, wherein the first precoding vector and the second precoding vector are either explicitly indicated or determined, or derived based on one or more conditions.